This invention relates to improvements in the continuous winding of flexible web materials and in particular to an improved apparatus and method for driving the cores on which the material is wound in a flying transfer winder wherein the web is transferred from a fully wound roll to a new core without stopping the flow of the material being wound. The invention is applicable to winders wherein the core driving means are controlled by a dancer roll system upstream of the winder, such means being well known in the art as exemplified in U.S. Pat. Nos. 2,509,250 to Roberts, 2,237,112 to Parvin, 2,886,257 to Hill, 3,650,490 to Saunders and many others.
The term "flying transfer winder" as used herein includes those winders in which the traveling web is transferred from the fully wound roll to a new core without stopping the flow of the web material being wound. The preferred embodiment includes a mechanical transfer device which severs the moving web and starts the leading edge on the new core, with or without the use of adhesive. Such devices are well known and of various types, typical of which are those disclosed in Meihofer U.S. Pat. No. 3,383,062, Phelps U.S. Pat. No. 2,943,806 and Kohler U.S. Pat. No. 2,586,832. In addition the term "flying transfer winder" as used herein includes those winders wherein the transfer is accomplished manually by the winder operator severing the web with a knife or other severing means and manually starting the leading edge of the web on the new core.
One of the requirements associated with flying transfer winders is that speed and torque delivered to the new core immediately before, during, and immediately after the transfer of the web to the new core be precisely regulated in order that the transfer be positive and that the tension in the web is maintained substantially constant throughout the transfer. It will be appreciated that at the moment of transfer the core on which the completed roll is winding is turning slowly because of the large roll diameter relative to the rotational speed of the small diameter new core required to substantially match the linear speed of the web.
Piperoux U.S. Pat. No. 2,718,362 discloses a flying transfer winder wherein the core drives are controlled by a dancer roll system and wherein two independent drive motors are used, each motor driving an associated core. By this means it is possible to bring the new core up to or slightly below the linear speed of the web before the transfer is made so that upon transfer and switching of the dancer roll control to the new core there is a minimum of disturbance to the web tension. Meihofer U.S. Pat. NO. 3,383,062 is similar with the addition of overrunning clutches in the core drives to improve the operation.
Due to the characteristics of the winding process, wherein the drive motor must provide low torque at high speed at the start of winding and high torque at low speed at the finish when the wound roll is full in order to maintain the desired web tension, the winding motors are costly and it therefore would be desirable to provide a flying transfer winder which operates with only one dancer controlled winder drive motor.
Kohler U.S. Pat. No. 2,586,832 discloses a flying transfer winder wherein only one winder drive motor is required and where an auxiliary drive is used to import rotation to the new core before transfer; this rotational speed being somewhat above the speed of the web. This method is satisfactory, as is stated in the patent when the motor accelerates very rapidly to its full speed with the removal of the load. However, this will not occur when the winder drive motor is controlled by a dancer roll since at the instant of transfer, the dancer roll is in a position calling for slow speed of the winder drive motor. The motor will therefore not accelerate until the dancer roll moves to a new position calling for high motor speed. This movement will not occur using the method of Kohler since the new core is driven faster than the web and after transfer the web speed will increase, moving the dancer roll in the direction of calling for a slower speed of the motor, rather higher speed.
Phelps U.S. Pat. No. 2,943,806 provides an auxiliary drive which brings the new core up to match the web speed. In a dancer roll controlled system this would result in the dancer roll maintaining its position calling for slow speed of the winder drive motor.